NH4+ TRANSPORT IN RENAL INNER MEDULLARY COLLECTING DUCT

NH4 在肾内髓质收集管中的转运

基本信息

批准号：
2749629
负责人：
SUSAN MARIE WALL
金额：
$ 16.72万
依托单位：
UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
依托单位国家：
美国
项目类别：
财政年份：
1997
资助国家：
美国
起止时间：
1997-08-01 至 2001-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/2749629
关键词：
acidity /alkalinity ammonia bicarbonates carbonate dehydratase carbonic anhydrase inhibitors cellular polarity hormone regulation /control mechanism mineralocorticoids ouabain renal tubular transport sodium potassium exchanging ATPase tissue /cell culture western blottings

项目摘要

The collecting duct plays a major role in the excretion of total ammonia (NH3 and NH4 plus), the major regulatable component of urinary net acid excretion. Ammonium (NH4plus) secretion by the collecting duct is attributed to active proton secretion in parallel with the passive diffusion of NH3. However, our laboratory has demonstrated direct NH4plus transport in the terminal inner medullary collecting duct (tlMCD). We have shown that NH4plus and Kplus compete for a common binding site on the Naplus minus- ATPase and that inhibition of the Naplus pump decrease transepithelial net acid secretion through blockade o Na plus minus pump mediated NH 4 plus transport. Uptake of NH4 plus across the basolateral membrane of the tlMCD by the Naplus minusKplus - ATPase, provides a source of Hplus for luminal acidification and the titration of other luminal buffers. Unlike the m ore proximal collecting duct segments, in the tlMCD interstitial and luminal NH3 and NH4plus concentrations have been measured. Thus, transporter mediated NH4plus flux can be placed in context with known NH3 and NH4 plus gradients to determine the physiological role for Na plus pump-mediated NH 4 plus transport. However, it is not known if changes in Na plus pump activity in vivo regulate transepithelial net acid secretion. If net acid secretion across the apical membrane is increased following in vivo conditioning, it is expected that across the basolateral membrane net Hplus uptake or OH/HCO3 exit would increase in parallel. This project will determine if Na plus pump number and Na plus pump-mediated ion transport are regulated by aldosterone administration in vivo. We will then test if Na plus pump activity increases, in parallel, with both total and ouabain-sensitive NH4 plus uptake and transepithelial net acid secretion. Hence, we will establish if changes in NH4 plus uptake in vivo regulate net acid secretion. Aims of this proposal are to determine the following in the rat tlMCD: 1) If mineralocorticoid increases Na plus, K plus -ATPase-mediated ion transport and Na plus pump number. 2) If mineralocorticoid increases NH 4 plus uptake across the basolateral membrane. 3) If mineralocorticoid increases total and ouabain-sensitive net acid secretion and 4) If mineralocorticoid stimulates other basolateral H plus or OH/HCO3 transport pathways, providing a source of protons for apical secretion. The aims will be addressed using isotopes and immunoblots of tlMCD cells in suspension. Observations will be extended using tlMCD tubules perfused in vitro.

集合管在总的排泄中起重要作用氨（NH3 和 NH4 加），主要可调节成分尿净酸排泄。铵 (NH4plus) 的分泌集合管归因于平行的主动质子分泌 NH3 的被动扩散。不过我们实验室有展示了航站楼内部的直接 NH4plus 运输髓质集合管（tlMCD）。我们已经证明 NH4plus 和 Kplus 竞争 Naplus 上的共同结合位点 ATP 酶和 Naplus 泵的抑制减少通过阻断 o Na 加减的跨上皮净酸分泌泵介导的NH 4 plus 运输。 NH4+ 的吸收 Naplus minusKplus 的 tlMCD 基底外侧膜 - ATPase，为管腔酸化提供 Hplus 来源其他管腔缓冲液的滴定。与更近端的集合管段，位于 tlMCD 间质和腔内 NH3 和 NH4plus 浓度均已测量。因此，转运蛋白介导的 NH4plus 通量可以置于以下背景中已知 NH3 和 NH4 加梯度来确定生理学 Na+泵介导的NH 4+ 运输的作用。然而，它尚不清楚体内Na+泵活性的变化是否调节跨上皮净酸分泌。如果净酸分泌穿过顶膜在体内调节后增加，预计穿过基底外侧膜净 Hplus 摄取或 OH/HCO3 排出量将平行增加。该项目将确定 Na 加泵数和 Na 加泵介导离子转运受体内醛固酮给药的调节。我们然后将测试 Na + 泵活性是否同时增加总 NH4 和哇巴因敏感 NH4 加摄取和跨上皮净酸分泌。因此，我们将确定 NH4+ 是否发生变化体内摄取调节净酸分泌。本提案的目的要确定大鼠 tlMCD 中的以下内容： 1) 如果盐皮质激素增加Na+、K+-ATP酶介导的离子运输和 Na 加泵数。 2) 如果盐皮质激素增加穿过基底外侧膜的 NH 4+ 吸收。 3）如果盐皮质激素增加总酸和哇巴因敏感的净酸分泌和 4) 如果盐皮质激素刺激其他基底外侧 H plus 或 OH/HCO3 运输途径，提供质子用于顶端分泌。这些目标将通过以下方式实现：悬浮液中 tlMCD 细胞的同位素和免疫印迹。将使用 tlMCD 小管灌注来扩展观察体外。